Maybe this helps:

my $C='((w)hite|(b)lack)';

my @c;
my @d;
while (<DATA>) {
    if (/$C\s+"princepawn"/i) {
        push @c, [ // ];
        push @d, [ $1, $2 || $3 ];
    }
}

use Data::Dumper;
print Dumper(\@c); # What you said
print Dumper(\@d); # ['black', 'b'] or ['white', 'w']
__DATA__
white "princepawn"
foo
black "princepawn"
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About popping and pushing strings:

sub popstr   { substr $_[0], -1, 1, '' } # or chop
sub shiftstr { substr $_[0],  0, 1, '' }
sub pushstr    { length($_[0] .= join '', @_[1..$#_]) }
sub unshiftstr { length($_[0]  = join('', @_[1..$#_]) . $_[0]) }

my $string = 'testing';
my $foo = shiftstr $string; # esting
my $bar = popstr $string;   # estin
pushstr $string, $foo;      # estint
unshiftstr $string, $bar;   # gestint
print "$string\n";
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Or, using regexes:

sub popstr   { $_[0] =~ s/(.)\z//s; $1 }
sub shiftstr { $_[0] =~ s/^(.)//s;  $1 }
sub pushstr    { $_[0] =~ s/\z/join '', @_[1..$#_]/e; length $_[0]; }
sub unshiftstr { $_[0] =~ s/^/join '', @_[1..$#_]/e;  length $_[0]; }

my $string = 'testing';
my $foo = shiftstr $string; # esting
my $bar = popstr $string;   # estin
pushstr $string, $foo;      # estint
unshiftstr $string, $bar;   # gestint
print "$string\n";
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2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
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